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Non-heavy-metal ZnS quantum dots with bright blue photoluminescence by a one-step aqueous synthesis
Please use this identifier to cite or link to this item:
http://hdl.handle.net/1860/1665
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| Title: | Non-heavy-metal ZnS quantum dots with bright blue photoluminescence by a one-step aqueous synthesis |
| Authors: | Li, Hui
Shih, Wan Y.
Shih, Wei-Heng |
| Issue Date: | Apr-2007 |
| Publisher: | Institute of Physics |
| Citation: | Nanotechnology, 18(20): pp. 205604-1 - 205604-6. |
| Abstract: | We have examined the aqueous synthesis of non-heavy-metal ZnS quantum
dots (QDs) using 3-mercaptopropionic acid (MPA) as the capping molecule
at various pH and MPA:Zn:S ratios. Transmission electron microscopy
(TEM) and x-ray diffraction (XRD) indicated that the aqueous ZnS QDs
were 3–5 nm in size with a zinc blende structure. We showed that, at pH 12
with a MPA:Zn:S = 8:4:1 ratio, the ZnS QDs with optimal blue emission
could be obtained in a one-step, room-temperature aqueous process that
exhibited a quantum yield of 31%, higher than that of the commercial
CdSe/ZnS core–shell QDs. The present ZnS QDs could pass through a 50 kD
filter. This indicated that they were smaller than 5 nm in size, consistent with
those estimated from the UV–vis absorption edge and the TEM image. At a
lower pH (e.g. pH = 8), the room-temperature synthesized ZnS QDs
exhibited no photoluminescence. Although further hydrothermal annealing at
100 ◦C could improve the photoluminescence of the ZnS QDs, the resultant
emission was not as bright as that obtained at pH 12 at room temperature.
The blue emission of aqueous ZnS QDs was likely the result of trap-state
emissions involving the defect states of the QDs. The present ZnS QDs were
bright, small and contained non-heavy-metal elements, thus offering the
potential for in vivo bioimaging. |
| URI: | http://dx.doi.org/10.1088/0957-4484/18/20/205604
http://hdl.handle.net/1860/1665 |
| Appears in Collections: | Faculty Research and Publications (MSE)
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